Method of quantitatively analyzing gas mixtures of known constituents and apparatus therefor.



. H. GIE'RDIEN.

METHOD OF QUANTITATIVBLY ANALYZING GAS MIXTURES 0F KNOWN GONSTITUBNTSAND APPARATUS THEBEFORJ APPLICATION FILED JULY 18, 1913.

1,133,556,. Pater lted Mar. 30, 1915.

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is H. GERDIBN. MBTHQD 01-" QUANTITATIVELY ANALYZING GAS MIXTURES 0FKNOWN GONSTITUENI'S AND APPAfiATus THEREFOR.

APPLIUATION FILED JULY 18, 1913.

1,133,556, Patented Mar. 30, 1915.

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@M w/fiv/p I @11 3? HANS GERDIEN, OI HALENSEE, NEAR U ITED STATES PATENTOFFICE BERLIN, GERMANY, ASSIGNOR TO SIEMENS &

HALSKE A. (3., OF BERLIN, GERMANY, A CORPORATION OF GERMANY.

OF KNOWN CONSTITUENTS Specification of Letters Patent.

Ifatented Mar. so, 19115.

Application filed July 18, 1913. Serial No. 779,883.

T all whom it may concern:

Be it known that I, HANS GERDIEN, a subject of the German Emperor, andresident of Halensee, near Berlin, Germany, have invented certain newand useful Improvements in Methods of Quantitatively Analyzing GasMixtures of Known Constituents and Apparatus Therefor, of which thefollowing is a specification.

My invention, broadly speaking, consists therein that I impart a rotarymotion to the gas-mixture to be analyzed, thus creating an increase ofgas-pressure from the center toward the periphery of rotation and inthat I utilize this increase of pressure for immediately determining thequantity of each constituent of the gas-mixture. This increase ofpressure, as well known, may be caused by a centrifuge, by a stowingdisk or a similar device which is moved with a known velocity againstthe gas. In this specification and the annexed drawings I have confinedmyself to centrifuges for obtaining the effect of generating suchressures of gases, while it is understood that I may employ any otherequivalent device. In case the centrifuge is used the pressure isadvantageously taken between two points of which one is located near thecenter and the other in proximity to the periphery of rotation, and theincrease 0f-pressure 1s measured in the well-known manner, for instancebya U-shaped tube filled with mercury. The mercury column then willadjust itself according to the difference of pressure and the differencein the height of the mercury in either shank of the U-shaped tube willthen at a given velocity of rotation be dependent upon the constituencyof the gasmixture.

In order to explain more fully the theory of my present invention I wishto state as follows :Acc0rding to the experiments of Bredig and Haber,man periodical Zeitschrift fiir Angewandte Chemie, volume 17, pages452464, the following relations hold true for gases under the action ofcentrifugal forces In this formula Mvis the molecular weight, g), and p,are the pressures in the rotating as described in the Gergas at the axisand at the distance 1', respectively, o is the velocity at tlie distancer, R the gas-constant and T the absolute temperature. From this it maybe followed that for a second gas which is simultaneously subjected tothe rotation the following relation must also hold true Mo p 2 RTZn Inthis formula the pressure taking place at the distance 1" in thegas-mixture is equal to the sum of the individual pressures p and p andthe pressure at the axis is equal to the sum of the individual pressuresp and pa At small velocities v at which, according to experience, noappreciable separation of the individual constituents of the gasmixturetakes place, and therefore no appreciable difference exists between 1),:1), and 1),, 110,, the measure of the difference in pressure between apoint near the axis and a point at the distance r from the axis may beused for measuring the average molecular weights of the gas-mixture, andin case the molecular weights of the individual constituents are knownfor indicating the quantity of each constituent of the mixture. If, forinstance, the gas-mixture contain two different constituents, whosemolecular weights are respectively designated with M and M their volumeper cents in the mixture with a and B, and the difference in the heightof the mercury columns with a, then we will obtain the relation (1.11,,[iM ice in which is is a constant. Since eel-5:100, the quantities ofthe mixture of each gas may be determined from these two equations. Agraduation maybe made upon the Ushaped tube permitting to read thecontents of each individual gas of each gasmixture. If a gas-mixturecontain more than two constituents this method may be carried out insuch a manner that first the difference of the pressure of the entiremixture is determined, and thereupon one constituent is absorbed by anabsorbing medium, thereupon for the remainder having now only twoconstituents, the difference in pressure and therewith the constituencyis also determined. The difference of pressure for the absorbedconstituent can then be indicated from the other differences ofpressure, which have been measured, and so forth. Also the gas-mixtureto be analyzed, if containing more than two constituents, may-be dividedand one part led through an absorbing apparatus and thereupon intov thedevice for generating the difference of pressure, while the other partis directly led into a centrifuge, whereby a resistance may-be insertedinto the connecting tube to the centrifuge, said resistancecorresponding to the resistance and contents of the absorbing vessel. Inthis manner I obtain in either centrifuge differences of pressurecorresponding to quantities of gas which are simultane ously taken off.

Besides other purposes, this method may be applied for analyzingsmoke-gas, generator-gas or furnace-gas. In such cases also arrangementsmay be provided for leading the gas through the apparatus in acontinuous stream, or also samples of the gas may be taken at intervals.

In order to convey. the gas-mixture through the centrifuge ascontinuously as possible, without causing'it to exert an objectionablesucking action thereupon, a choking device is preferably inserted intothe tube leading: from the centrifuge. In this case always only such aquantity of gas is carried into the centrifuge as can be pressed forwardby the choking device.

For rendering the indications independent from pressure and temperatureand indicating the result of the measurement in a very simple manner andto avoid corrections and re-checking a test gas or standard gas having aknown molecular weight is set in rotation in a second container inunison with the container for the mixture to be analyzed, while bothgases are maintained at even temperature and under even pressure. Eventemperature, 6. g. may be obtained by leading either gas through acooling vessel before being conveyed into the analyzing apparatus andpreferably maintaining the latter also upon even. temperature. Evenpressure may be attained by causing both gases to'act upon differentsides of the membrane, which will yield to the action of the higherpressure until the equilibrium takes place between the gas pressures.Another way for securing even pressure is to have the openings of bothcentrifuges discharge into a common discharge pipe or into the open air.The differences of pressure in the two centrifuges in which the gasesare set in rotation are now transmitted upon an indicating mechanismwhich directly indicates the ratio of the differences of pressure.

I am aware that it is known to indicate the difference of twopressures-that is to say the arithmetical difference of gas pressures atdifl erent distances from the center of rotation-in a single apparatus.In the present case, however, the quotient of such differences ofpressure has to be indicated. If, for instance, the difference ofpressure of one gas be 19 -12 andthe difference of the other gas may beP y-"P21 then the quotient P1 p2 is the quantity which shall bedetermined according to my present invention. This quotient correspondsto the ratio of the molecular weights, and if a gas with known molecularweight be taken as a basis, then the average molecular weight of thegas-mixture to be analyzed will be immediately obtained. The ratios ofthe differences of pressure can be indicated in a number of ways and maybe accomplished mechanically or electrically. The two differences ofpressure may, for instance, be caused to act upon membranemanometers orupon manometers containing a liquid and a float, or upon gasometercontainers which are connected with a rectangular bell-crank having twoeven arms in a manner to act as parallel forces thereupon.

As a great part of the motions of the membrane will be taken up by theresilient connections to the bell-crank the points of attack at thebell-cranks make only a small motion and the directions of the points ofattack at the bell-crank will therefore practically remain parallel toeach other. The motion of the bell-crank is transferred mechanicallyupon a scale or may also be automatically recorded. Instead of abell-crank, according to the laws of-mechanics also a straightdouble-lever with even arms may be employed, upon which the forces actrectangular to each other for indicating the ratio of said forces. Theratios of the differences of pressure may also be indicated electricallyby an electrical quantity, such as resistance voltage or currentstrength, which is made to vary as a function of the difference ofpressure, and the variations of this electrical quantity may betransferred upon an instrument for indicating the ratio of twoelectrical quantities, for instance upon an instrument ofthe dArsonvaltype having two coils crossing each other at right angles.

My invention will be more fully understood by reference to theaccompanying drawings of which- Figure 1 shows an arrangement of twocentrifuges which are driven in unison, one being used for a standard ortest gas, the other for the gas-mixture to be analyzed, the ratio of thedifferences of pressure being transmitted upon an indicating device,Fig. 2 a modification of the indicating device of Fig. 1, Fig. 3.2marrangement whereby the indication of the constructions of Figs. 1 or 2is obtained electrically, Fig. 4 a modified form of the electricalscheme shown in Fig. 3 and of'whichFig. 5 is a modification of thearrangement of Fig. lin that .a regulation is-employed for the speed ofthe centrifuges in dependence from the pressure of the. standard or testgas.

Referring now more particularly to the drawing, in Fig. 1 a and b aretwocentrifuges mounted upon a common axle 0. Through the centrifuge a Iconvey the gasmixture to *be analyzed and through the centrifuge b thestandard or test gas. Both gases are setiin rotation and thereby apressure-difference is generated between points at a difi'erent distancefrom the center of rotation. Assuming the gases to be discharging intothe open air at d and e the pressureat the periphery atthe rotatingapparatus will be equal to the atmospheric pressure. A difference ofpressure, therefore, will manifest itself as under-pressure relativelyto the atmosphere and may be transmitted through the pipes f and 9 intotwo containers h and 7 which are closed by membranes is and m,respectively. These membranes will yield under the action of thepressures and transfer their motions through resilient connections suchas n and 0 upon a rectangular bell-crank p having arms of even length,said bell-crank carrying at its center, as shown in Fig. 1 of the Ydrawing, a pointer for indicating the ratio of the abovepressure-diflerences. Instead of directly transmitting the motions ofthe membranes 7c and m upon a pointer, of course, .further gears for'magnifying the motions of the membranes or the deflections of thebell-crank may be interposed. The bell-crank p of Fig. 1 may be replacedby a double-lever g of Fig. 2 having even arms, and the forces must thenbe made to attack rectangular to each other. This modificatidn is shownin Fig. 2'. In this figure the resilient connection 0 between themembrane m remains unchanged from that of Fig. 1. The resilientconnection at of the membrane is, however, is made to attack upon theend of the arm of the-lever g-rectangularly to the direction of attackof the connection 0, by providing a roller :1 over which a cord 3 isstrung in such a way that the end of this cord which is connected to thelever 2 is rectangular to the direction of the forces exerted by themembrane is, namely to the direction of the connection n.

The deflections of this device also will indi-.

cate the ratio of the differences of pressure. In Fig. 3 I have shown anarrangement in which the ratio of the difl'erences of pressure will beindicated electrically. In this case again thegas to be analyzed and thestandard or test gas are carried from the centrlfuges into twomembrane-manometers k, and 6,, respectively. Sliding contacts 1'and-rare connected with the membranes la and =m, respectively, saidsliding contacts contacting with the resistances t and u.

The resistances are traversed by a constant current from the battery 4)and the sliding contacts will thus take up the voltage at the resistanceat a time included by the sliding contacts and impress the same upon thecoils of the 'dA-rsonval instrument w.

Instead of the variations of voltage of a circuit 5 by resistance andsliding contacts another arrangement may be employed especially' forhigher pressures, such arrangement being shown in Fig. 4. Thedifferences of pressure of the two centrifuges a, and b, aretransmitted. through pipes 03,, e and'f 9 into two. .U-shaped tubes 1and 2 which are filled with mercury. .In one shank of either U-shapedtube a resistance wire 3 and 4 is provided, the ends of either wire 3and i being connected with one of the coils of a dArsonval instrument10, over the battery 0 as shown in the drawing. According to the'heightof the two mercury columns in the shanks which carry the resistancewire, the free length of the resistance wires will apparently be'changed and therewith the resistance of the circuits, the ratio'of theseresistances and therewith the ratio of the pressure-differences of thetwo gases being then indicated by the instrument.

Another very practical mode of indicating the quotient ofpressure-differences of two gases consists in adjusting the speed of thecentrifuges to maintain constancy of the pressure of the standard ortest gas so that the deflection of the manometer for the test gasassumes a definite value. The manometer for theother gas may then becalibrated according to molecular weights.

providing a regulating means or governor for regulating the speed of thecentrifuge in dependence from the position of the indicating device ofthe standard or test gas, for instance in such a way that the pointerof=the indicating device'can move-between two, contacts in a smalldistance from each other, so that by closing the one or'the othercontact the speed'of the driving motor for the centrifuges will beincreased and decreased,'respectively. In this case a definiteadjustable difference of pressure at the manometer of the standard ortest gas will be maintained independently from the fluctuations ofpressure and temperature. If care be-taken that the other gas rotatingaround the same axle is kept uhder the same pres- I This scheme-may bereduced to practice by Fig. 5 of'the drawing an arrangement of this kindis shown diagrammatically. A centrifuge Z), for the gas to be analyzedand a centrifuge a for the test or standard gas are mounted upon acommon axle which is driven by a motor 5. At 10 and 11 these gases areled into the centrifuges, it being assumed that for the sake ofsimplicity the gases after having been centrifuged exhaust into theatmosphere at 12 and 13, so that the pressure at .the entrance of thecentrifuges will be equal to the atmospheric pressure which exists atthe entrance of the centrifuge and therefore also equal to theatmospheric pressure itself. The gases which are conveyed at 8 and 9 tothe indicatingdevice will then be at an under-pressure relatively to theatmosphere. The gases are conveyedinto containers h and i which areclosed by membranes is and m, respectively. The motion of the membranesis transmitted upon pointers 14 and 15. The pointer 14: of theindicating apparatus for the standard or test gascan play between twoclosely adjacent contacts 16 and 17. 18 is a battery and 19 a motorwhich by means of a threaded spindle 20 and nut 21 serves to insert agreater or smaller part of the resistance 22 into the field circuit ofthe driving motor 5. If, for instance, the contact 16 be closed by thepointer 14, the motor 5 will be so excited that the resistance will becut out of circuit, while if contact 17 be closed resistance will beinserted into circuit. driving motor 5 will accordingly be keptpractically constant or at most be subject to small fluctuations, andthe position of the pointer 15 with indicating apparatus for theprinciple or sacrificing any of the advantages of my invention.

I therefore claim and desire to secure by Letters Patent of the UnitedStates -1 Apparatus for quantitatively analyzing gas mixtures of knownconstituents, comprising in combination means for rotating a body of gasto develop difference The speed of the of pressure from the axisoutward, and means for directly observing this difference of pressurefor determining the quantity of each constituent.

2. Method for quantitatively analyzing a gas-mixture having knownconstituents, which consists in rotating said gas-mixture in unison witha test or standard gas, and indicating the quantity of each constituentof the mixture by the ratio of the difference of pressure of said testor standard gas to the difference of pressure of said mixture.

3. Method for quantitatively analyzing a gas-mixture having knownconstituents, which consists in imparting a rotary mo tion to saidgas-mixture to generate a difference of pressure therein and rotating atest or standard gas in unison with said gas mixture, maintaining eithergas at the same temperature and under the same pressure, and indicatingthe ratio of the diiferences of pressure of either gas for determiningthe quantity of each constituentof the mix-' ture.

4:. Method for quantitatively analyzing a gas-mixture having knownconstituents, which consists in imparting a rotary motion to saidgas-mixture and rotating a test or standard gas in unison therewith togenerate differences of pressure in either gas thereby, maintaininguniformity. of said rotary motion, andindicating the molecular weight ofsaid gas-mixture as a multiple of that of said test or standard gas.

5. Method for quantitatively analyzing a gas-mixture having knownconstituents, which consists in imparting arotary motion to saidgas-mixture and rotating a test or standard gas in unison therewith togenerate differences of pressure in either gas thereby, regulating thespeed of rotation of said gases upon a constant pressure of said test orstandard gas, and indicating the molecular weight of said gas-mixture asa multiple of that of said test or standard gas.

In witness whereof I have hereunto set my signature in the presence oftwo subscribing witnesses.

- HANS GERDIEN.

Witnesses WOLDEMAR HAUPT, HENRY HASPER.

